Means for describing circular and elliptic arcs.



J. A. CALDWELL.

MEANS FOR DESCRIBING CIRCULAR AND ELLIPTIC ARCS.

APPLICATION FILED FEB. 2| L9H- Patented June 26, 1917.

INVENTOR ATTORNEYS rm: NnRRIs PETERS co macro-1.1mm I wAsNmcmN, n. c.

JOHN A. CALDWELL, OF VANCOUVER, BRITISH COLUMBIA, CANADA.

MEANS'FOR DESCRIBING CIRCULAR AND ELLIPTIC ARCS.

Application filed. February 2, 1917.

To all whom it may concern:

Be it known that 1, JOHN A. CALDWELL, a citizen of the Dominion of Canada, residing at Vancouver, in the Province of British Columbia, Canada, have invented certain new and useful Improvements in Means for Describing Circular and Elliptic Arcs, of which the following is a specification.

This invention relates to certain attachments and connections to be used in conjunction with a tape-line, whether of steel or fabric, whereby that tape-line may be used for describing circular or elliptic arcs and as a substitute for the customary trainmel beam, the attachments being so made and connected that the graduations of the tape may be used to determine the radius.

The attachments by which these results are attained are particularly described 1n the following specification, reference being made to the drawings by which they are accompanied, in which:

Figure 1 shows the application of the device as used in describing a circle.

Fig. 2, as used in describing an ellipse.-

Fig. 3 shows in perspective the removable fixed pivot or center pin used either for the center of a circle or the foci of an ellipse, to which pin one or the other end of the tape-line is connected.

Fig. 4 shows in plan a pivot pin connection with a removable clamp which may be secured to any desired endwise position on the tape whereby the tape may be connected either to the fixed center pin shown in Fig. 3, or to the pin of the movable member shown in Figs. 4 and 5.

Fig. 5 is a perspective view of the same.

Fig. '6 is a plan view of a pivot pm attachment hereinafter referred to.

' Fig. 7 is a perspective of the pivot pin attachment with provision for connecting the loop end of the tape thereto. 7

Fig. 8 shows in section on the line in Fig. 9 the movable member of the device which is connected to the tape and which carries the pencil, pen or other scribing or cutting instrument, and I Fig. 9' is a plan of the same. In Fig. 1 of the drawing it willbejseen that the tape attachments are such as will enable a pencil 13 or other drawing or scribing instrument to be connected to the free or loop end of a tape-line 20 while a pivot bearing or sleeve may be securely clamped to any desired position of endwise Specification of Letters Patent.

Patented June 26, 1917.

Serial No. 146,140.

adjustment on the tape-line and mounted on a center pivot or spindle 2 about which the drawing instrument 13 may thus be moved with the intervening section of the tape-line 20 as a radius.

The fixed pivot comprises a pin having a finely pointed or screwed end 3 and a relatively wide collar 4 fixed to it adjacent the screwed end. The upper end of this pin 2 is screwed as at 5 to receive a milled nut 6 to retain in position a sleeve or other device mounted on the pin, and serving at the same time as an enlarged head by which the pointed end of the pivot may be pushed or screwed into a board on which it may be required to describe a certain curve. The relatively large diameter of the flange or collar 4 serves to insure that the pin will stand substantially normal to the surface. This pin 2 is used as the fixed center of a circle or as one of the foci for an ellipse, the other focus being the same.

The tape-line 20 is connected to this pivot pin 2 by either one of two devices: One connects the tape-line intermediate of its ends and provides a means by which it may be clamped at any desired position of endwise adjustment and the other provides a means whereby the end loop of the tape may be connected to it.

The first, see Figs; 4 and 5, comprises a sleeve 21 rotatable on the pivot pin 2 and having a clamp 22 through which the tape line maybe endwise passed and secured by means of a milled headed screw 23. This is generally used in describing arcs of circles book 19 projecting from the side of the .sleeve within the bend-of the hook at right angles to the radial face of the arm 16. This attachment'ispreferably used for connection of the tape to the instrument holding device, to be described, when drawing circular arcs or, when, describing elliptic curves, is used on a second pm- 2 on the other focus of the ellipse.

The instrument holding device comprises a substantially triangular slidable base 7 having a downwardly turned edge 8 along one side of the base and a thickened reinforcement 12 at the angle opposite the base. At this angle a portion 9 is upwardly turned at right angles to the base and may have a slight vertical groove in the middle line to maintain a pen or pencil in the upright po- 10 sition where such is to be used. .Any suit able drawing or scribing instrument is secured against the face of this upright 9 by a clamp 10 and a milled headed screw 11, and its drawing or scribing point adjusted to trace or mark the surface on which the base 7 is slidable.

Upwardly projecting from the middle line of the base 7 adjacent the instrument holding upright 9 is a pin 14, which pin corresponds in diameter and length to the fixed fulcrum pin 2 so that it may take either of the tape-line attachments 17 or 21. It is also provided with a small roller for use in describing elliptic curves.

25 Fig. 1 shows the application of the device to describe a circular arc: The fixed pivot pin 2 being secured in the board at the center of the desired are, the clamp of the sleeve 21 is passed onto the tape 20, and the loop end of the same is connected in the manner described to the other sleeve 17.

The sleeve 21 is then placed on the pivot 2 and retained in position by its milled nut 6, and the sleeve 16 to which the loop of the I tape is connected is placed upon the pivot 14 of the instrument holding member 7.

The point of the drawing instrument may then be set to the desired radius by adjusting the tape 20 lengthwise in the clamp 22 of the sleeve 21 and is secured in that adjustment by the clamp screw 23. Care being taken that the tape-line is maintained tight, the slidable instrument holding base 7 may be moved around the pivot 2 to describe the desired curve. :Fig. 2 illustrates the application of the device to describe an ellipse. The sleeve members 17 and 21 being connected to the tape-line 20 in the manner described, they are placed on pins 2 secured in the drawing board on the foci of the ellipse. The roller 25 being placed on the pin 14 of the slid able instrument holding member 7, this roller is placed in the loop of the tape 20 5 and the tape is adjusted lengthwise in the clamp 22 of the sleeve 21 to allow the point of the drawing instrument to be set to the end of either the conjugate or transverse axis of the ellipse, when the desired curve may be described. 15 is a milled nut for holding the roller 25 in place.

The device provides a simple and effective means for describing either circular or elliptic arcs and'is a complete substitute for 6 the customary trammel beam. The underside of the base 7 should be smooth and have its corners slightly rounded that it may slide freely over the surface of the board or paper. The broad surface of this supports the drawing instrument steadily in an upright position and if a steel tape is used and care is taken to maintain it tight, a very definite curve can be drawn, more so than with a trammel beam. The wide collar of the pin 2 not only insures that the pin 7 5 is at'right angles to the surface but supports it in the tension imposed on the tape.

The instrument clamp may obviously be used not only with any drawing instrument but with any suitable scribing or cutting in- 50 strument.

Having now particularly described my invention, I hereby declare that what I claim as new and desire to be protected in by Letters Patent, is:

1. A device for describing circular or elliptic curves, said device comprising the combination with a tape-line, of a sleeve having means for connecting the loop end of the tape adjacent the axis of the sleeve, 99

a second sleeve having means for slidably clamping the same at any desired endwise position on the tape, pivot pins adapted to receive the sleeve onthe tape and having provision for attachment to a surface to project at right angles from such surface, an instrument holding member comprising a slidable base with provision at one end for clamping a drawing or scribing instrument, at right angles to the plane of the base, and a pin projecting at right angles to the base adjacent the instrument, said pin adapted to fit either sleeve of the tape, and a roller adapted to fit the same pin. I

2. A device for describing circular or elliptic curves, said device comprising the combination with a tape-line, of a sleeve having means for connecting the loop end of the tape adjacent the axis of the sleeve, a second sleeve having means for slidably clamping the same at any desired endwise position on the'tape, pivot pins adapted to receive the sleeves of the tape and having pro vision for supporting them at right angles to the surface, an instrument holding device 115 comprising a substantially triangular base having a part upwardly turned at right angles thereto and adjacent one angle, a clamp for securing a drawing'or scribing instrument to the upwardly turned end, and a pin V upwardly projecting at right angles to the base adjacent the upwardly turned instrument holding portion, said pin adapted to receive either sleeve of the tape, and a roller adapted to fit the same pin. 3. A device for describing circular or elliptic curves, said device comprising the combination with a tape-line, of a pivot pin having a point for removable attachment to a board and a flange or shoulder secured on 139 it adjacent the point by which the pin is maintained substantially normal to the sur face of the board, an instrument holding member comprising a base, and means for securing an instrument at right angles to it, a pivot pin adjacent the instrument securing means, a sleeve adapted to fit the pin of the instrument holding member and having provision for removably connecting the loop end of a tape thereto, a second sleeve adapted to fit the fixed pivot pin and having means for clamping the tape thereto at any desired position of endwise adjustment on the tape, and a roller adapted to fit the pivot pin of the instrument holding member.

4. A device for describing circular or elliptic curves, said device comprising the combination with a tape, of a sleeve, an arm projecting from the sleeve in the plane of and radial to its axis, said arm having a slit at its end through which the end of the tape may be passed and a hook on the adjacent side of the sleeve, a second sleeve having a screw clamp by which it may be secured at any desired position of endwise adjustment on the tape, a pin adapted to fit either sleeve, said pin having a pointed end with a relatively wide collar adjacent thereto, and a nut threaded on its upper end, an instrument holding member comprising a slidable fiat base of triangular form turned down along the edge of one side and reinforced in thickness toward the opposite angle to the same depth as the turned down edge and having a portion at the angle opposite the base upwardly turned at right angles to the plane of the base, a clamp on the upwardly turned portion susceptible of securing a drawing instrument thereto, a pivot pin secured in and upwardly projecting from the base adjacent the upwardly turned portion, and a roller on the pin.

5. A device for describing circular or elliptic curves, said device comprising the combination with a tape-line, of a sleeve having an arm projecting from it and a hook on the side of the sleeve in a position at right angles to the face of the arm, means for holding the end of the arm in contact with the tape, a second sleeve having a clamp by which the sleeve may be secured at any position of endwise adjustment on the tape, a pivot pin adapted to fit either sleeve, said pin having means for securing it at right angles to a drawing surface, an instrument holding member comprising a slidable flat base having a portion upwardly projecting from one end provided with a clamp by which a drawing instrument may be secured to it, a pin secured in and upwardly projecting from the base adjacent the upwardly turned portion and a roller on the pin.

In testimony whereof I affix my signature.

JOHN A. CALDWELL.

Copies of vthis patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

